We picked up some take-off catless downpipes from a customers, and decided to put those on the car. The install is a little tedious because of the tight work space, but it's straightforward other than that. If you do it yourself, plan to replace the rear gaskets. The front gaskets are a hard ceramic type that can be re-used.
The rest of the exhaust is still stock, including the remaining main catalytic converters. The car picked up still more power -- another 12+ hp and 10 ft-lbs, with no change in the ECU mapping.
In the near future Cobb Tuning will have "Stage 2" ECU mapping intended for cars with modified exhaust systems. At that time we'll re-flash the car and get the car back on the dyno with the new ECU logic. We expect still more power from that change, and more when we upgrade the intercooler further down the road.
If you were looking closely at the picture of our shop staff working on the 335i above, you'd see the new Continental ExtremeContact DWS tires (in stock Sport Package fitment of 225/40R18 and 255/35R18) we put on earlier this winter. As you probably know, the Bridgestone RE050A Sport Package tires are...downright hazardous in cold weather. The Continentals were a HUGE improvement in the snowy weather we had, with decent grip in sub-freezing temps and snow or slush. They're fairly quiet, and they have a very comfortable ride. The price isn't bad, either. The one trade-off is that they are not run-flat tires, so in that sense we're flying without a net -- the 335i does not include a spare tire. We carry a small air pump and tire plug kit, although depending on where/when we broke down we might just call for a tow if it comes to that.